The present invention relates to an apparatus and a method for applying a viscous fluid, e.g., used in applying an adhesive onto a circuit board to bond electronic components to the circuit board.
Such an adhesive applying apparatus 30 as shown in FIG. 26 has conventionally been employed to apply an adhesive onto a circuit board to bond electronic components to the circuit board. The adhesive applying apparatus 30 includes an adhesive application head unit 15 which will be described later, a Y-table 20 loading the circuit board thereon to which the adhesive is to be applied and moving the circuit board in a Y-direction, an X-robot unit 21 moving the adhesive application head unit 15 in an X-direction orthogonal to the Y-direction, and a controller 22 controlling operations of at least the adhesive application head unit 15, Y-table 20 and X-robot unit 21.
As indicated in FIGS. 27 and 28, the adhesive application head unit 15 has three sets of application mechanism portions for extruding and applying the adhesive with compressed air. Each application mechanism portion comprises a syringe 2 in which the adhesive 13 is stored and from which a predetermined amount of the adhesive 13 is discharged from a nozzle 1 through the injection of compressed air, a compressed air feed system 9 for feeding the compressed air to the syringe 2, and a lift mechanism 3 for moving the syringe 2 up and down in a thicknesswise direction of the circuit board so as to apply the adhesive 13 discharged to a leading end of the nozzle 1 onto the circuit board. The compressed air feed system 9 is provided with a piping 10 connected to the syringe 2 for feeding the compressed air into the syringe 2, and a valve 11 for controlling the supply of the compressed air to the syringe 2. The lift mechanism 3 is provided with a lift shaft 4 coupled to the syringe 2 and allowing the compressed air to pass through the lift shaft 4, a lever S rotating about a supporting shaft 14 and having one end 5a coupled to the lift shaft 4 and the other end brought into contact with a driving shaft of a nozzle selection cylinder 7, a cam follower 6 set to the lever 5 in a state to be rotatable, and a cam 8 engaged with the cam follower 6. In the lift mechanism 3, when the cam 8 rotates, at the lever 5 where the cam follower 6 and cam 8 are brought into contact with each other by the nozzle selection cylinder 7, the one end 5a of the lever 5 rotates about the supporting shaft 14, thereby moving the lift shaft 4 in the above thicknesswise direction.
The conventional adhesive applying apparatus 30 constituted as above operates in the following manner.
Before the adhesive 13 is started to be applied to the circuit board, the application head unit 15 carries out a test application of the adhesive 13 on a test tape 16 as shown in FIG. 27. More specifically, the valve 11 of the compressed air feed system 9 operates for a predetermined time, thereby pressing a float 12 in the syringe 2 down by the supplied compressed air, and consequently the adhesive 13 stored in the syringe 2 is discharged by a predetermined amount from a leading end la of the nozzle 1. The nozzle selection cylinder 7 then acts thereby bringing the cam follower 6 and cam 8 of the lever 5 into contact with each other. As a result of the rotation of the cam 8, the one end 5a of the lever 5 rotates as described above, lowering the syringe 2 in the thicknesswise direction via the lift shaft 4. The adhesive 13 discharged to the leading end 1a of the nozzle 1 is hence applied onto the test tape 16. After the test application, the cam 8 rotates and the syringe 2 moves up to an original position.
An application state of the adhesive 13 at the test application is picked up by a recognition camera 19. The controller 22 measures an area of the test application on the basis of image information output from the recognition camera 19, thereby judging whether or not a preliminarily set target-application-diameter is satisfied. The above test application and image pick-up operation are conducted until a diameter of the test application is kept within an allowance of the target-application-diameter. The adhesive 13 is started to be applied to the circuit board after the diameter of the test application is within the allowance of the target-application-diameter.
In the conventional adhesive applying apparatus 30 as above, as the amount of the compressed air supplied to the syringe 2 increases, the adhesive 13 in the syringe 2 decreases. The application diameter becomes smaller in accordance with a decrease of the adhesive 13 in the syringe 2 if the adhesive 13 is extruded with the same amount of air and the same pressure of the air at all times. so, in order to obtain a constant application diameter irrespective of the amount of the adhesive 13 remaining in the syringe 2, it is not enough to simply control the pressure of the compressed air and the amount of the air supplied to the syringe 2. The pressure of the compressed air and the amount of the air are required to be controlled also in accordance with a temperature of the adhesive 13 and a state of the test tape 16. Furthermore, these four conditions, namely, the pressure of the compressed air, the amount of the air, the temperature of the adhesive and the state of the tape should be selected for each kind of the adhesive and for each nozzle to be used in the conventional apparatus 30. Therefore, not everyone can handle the conventional adhesive applying apparatus 30. The conventional apparatus consumes much time in discharging the adhesive, and exhibits a loss of a cycle time in correcting the application diameter.
An apparatus disclosed in U.S. Pat. No. 5,564,606 proposes a solution to the above problem. According to the disclosed apparatus as shown in FIG. 29, a screw 33 is fitted to a sleeve 34 in a state where the screw can be rotated about an axis thereof by a motor 32 and, a nozzle 31 is disposed coaxially with the screw 33. A viscous material is supplied to the sleeve 34 through a path 35, sent to the nozzle 31 as a result of the rotation of the screw 33 about the axis, and discharged from a leading end of the nozzle 31. A constituting portion including the nozzle 31 is moved in an axial direction of the nozzle 31, whereby the viscous material discharged from the leading end of the nozzle 31 is applied to a member.
Since the above apparatus is adapted to discharge the viscous material through the rotation of the screw 33, the aforementioned problem caused by the amount of the remaining viscous material is eliminated.
As indicated by a chain double-dashed line, FIG. 29 also proposes another type of the apparatus, wherein a nozzle stopper 36 is erected at a portion of the sleeve 34 to form a predetermined gap between the leading end of the nozzle 31 and a face of the circuit board, for instance, when the viscous material is applied to the circuit board. The nozzle stopper is set adjacent to the nozzle 31, having a slightly larger length than a total length of the nozzle 31, with a leading end of the nozzle stopper 36 maintained in contact with the face of the circuit board.
However, an arrangement position of the nozzle stopper 36 relative to the nozzle 31 cannot be changed in the above prior art of the screw type equipped with the nozzle stopper 36. when the nozzle 31 moves in the axial direction to apply the viscous material, the leading end of the nozzle stopper 36 comes into contact with a wiring pattern, etc. formed on the face of the circuit board, and possibly damages the wiring pattern, etc.
The present invention is devised to solve the above-described problems, and has for its object to provide an apparatus and a method for applying a viscous fluid, which enables anyone to handle the apparatus with ease while obtaining a constant application diameter without a cycle time loss and with less possibility of damaging a surface of a member to which the fluid is to be applied.
According to a first aspect of the present invention, there is provided an apparatus for applying a viscous fluid which comprises:
a viscous fluid application member which receives a viscous fluid and has a nozzle for discharging the viscous fluid from one end thereof;
a discharge shaft for sending the viscous fluid in an axial direction of the nozzle when the discharge shaft is rotated by a discharge shaft-rotating device in a direction about an axis of the nozzle, while the discharge shaft is inserted within the viscous fluid application member and is parallel to the axial direction, wherein the viscous fluid application member is rotatable in the direction about the axis of the nozzle, to thereby discharge the viscous fluid from the one end of the nozzle so that the viscous fluid is held at the one end of the nozzle;
a nozzle-moving device for moving the viscous fluid application member in the axial direction of the nozzle, to thereby apply the viscous fluid held at the one end of the nozzle to an object; and
a viscous fluid application member-rotating device for rotating the viscous fluid application member in a direction about a central axis of the discharge shaft in accordance with an application condition for the viscous fluid to the object.
A Viscous fluid-applying apparatus according to a second aspect of the present invention may be provided with a discharge prevention device for preventing the viscous fluid from being discharged from the one end of the nozzle when the viscous fluid application member is rotated by the viscous fluid application member-rotating device.
In a viscous fluid-applying apparatus according to a third aspect of the present invention, the discharge prevention device is a control device controlling an operation of the discharge shaft-rotating device, thereby rotating the discharge shaft about the axis thereof in a rotation direction and by a rotation amount so that the viscous fluid is prevented from being discharged from the one end of the nozzle when the viscous fluid application member is rotated by the viscous fluid application member-rotating device.
The control device controls the operation of the discharge shaft-rotating device, thereby rotating the discharge shaft about the axis thereof in a rotational direction and by a rotational amount so that the discharge shaft does not rotate about the axis thereof relative to the rotation of the viscous fluid application member.
In a method for applying a viscous fluid according to a fourth aspect of the present invention, there is provided a method for applying a viscous fluid which comprises:
rotating a discharge shaft in a direction about an axis thereof in a manner such that a viscous fluid is prevented from being discharged from one end of a nozzle when a viscous fluid application member, into which the discharge shaft is inserted and parallel to an axial direction of the nozzle, and in a manner to be rotatable in a direction about an axis of the discharge shaft in accordance with an application condition for the viscous fluid to an object, thereby discharging the viscous fluid from the one end of the nozzle so that the viscous fluid is held at the one end of the nozzle; and
applying the viscous fluid discharged and held at the one end of the nozzle to the object when the one end of the nozzle comes into contact with the object.
As is fully described above, according to the viscous fluid applying apparatus in the first aspect of the present invention, the apparatus is constituted to discharge the viscous fluid from one end of the nozzle through the rotation of the discharge shaft in a direction about the axis thereof, and is provided with the viscous fluid application member-rotating device. Accordingly, the viscous fluid application member can be rotated in the direction about the axis of the discharge shaft to cope with application conditions, e.g., an increase of a number of application points of the viscous fluid, an interference preventive arrangement for a member to which the viscous fluid is to be applied, and the like. Thus, a possibility of damaging a surface of the member which the viscous fluid is to be applied is decreased.
According to the viscous fluid applying apparatus of the second aspect and the viscous fluid application and method of the fourth aspect of the present invention, the discharge prevention device is provided so that the viscous fluid is prevented from being discharged from the nozzle when the viscous fluid application member is rotated in the direction about the axis of the discharge shaft. Therefore, an excessive amount of viscous fluid affecting the application amount is never accumulated at one end of the nozzle, thereby improving accuracy of the application diameter. In particular, when the viscous fluid is to be applied in the same application size for a plurality of times, since the excess accumulation of the viscous fluid is eliminated, the amount of the viscous fluid discharged from the one end of the nozzle through the rotation of the discharge shaft in the direction about the axis thereof can be kept uniform at all times. In other words, a constant application size is obtained at all times.
According to the viscous fluid applying apparatus of the third aspect of the present invention, since the control device is provided which controls the rotation of the discharge shaft in the direction about the axis thereof, correspondingly to physical properties of the viscous fluid, the application operation for the viscous fluid of the required application size can be carried out automatically, allowing any worker to handle the apparatus easily.